The present invention relates to telemetry systems in general and more particularly to telemetry systems for medical purposes.
Telemetry is generally defined as a (more or less automated) communications process by which measurements are made and/or other data collected at remote or inaccessible points, and transmitted to a receiving equipment for monitoring, display, and/or recording. Originally, the information was sent over wires, but modern telemetry systems more commonly use radio transmission. Basically, the communication process is the same in either case. Among the major applications are monitoring electric-power plants, gathering meteorological data, monitoring manned and unmanned space flights, and more and m ore medical applications such as pulsoximetry or electrocardiography.
Telemetry systems normally comprise a transmitter for transmitting electromagnetic signals, e.g. from a measurement, and a receiver for receiving the electromagnetic signals from the transmitter. In current medical telemetry systems, the transmitter is usually carried by the patient and the receiver is typically installed in an operator room. Large systems may have a multitude of transmitters and receivers.
Patient monitoring with telemetry system gets more and more popular in many medical areas. Monitoring by telemetry has some advantages over conventionally monitoring especially for patients who need not necessarily stay in their bed but nevertheless must be monitored continuously. Advantages are present from a medical point of view as well as for the patient comfort.
For such a medical telemetry system with one or more transmitters and a multi-channel or multi-parameter receiver for a continuous wireless monitoring of one or more physiological parameters, it is desired to have a clear assignment and labeling of each transmitter and receiver channel, in particular for the following reasons:                For each transmission channel, display elements are provided on the receiver showing the actual status of the link and/or status and possible parameter information of active transmitters. A clear relation between the display elements on the receiver and the corresponding active transmitters allows an easy operation of the system. Comprehensible display elements are required especially in case of failure to allow an easy identification of faulty or disturbed transmission channels. Possible failures could be empty batteries in the transmitters, technical defects in the transmitter or receiver channel or interfering signals.        There might also be more than one patient in a room, and therefore more than one telemetry system can be active at the same time. A clear and easy identification of which transmission channel belongs to which patient and to which transmitter is required.        The same applies if a multi-channel receiver, which has several independent receiver channels in one unit, is used. Such a receiver is used to receive different transmitter signals to monitor several physiological signals from one patient or to receive different signals from different patients simultaneously.        
In most known telemetry systems, a static labeling of transmitters and receiver channels (e.g. with adhesive printed labels) is used to solve the assignment and identification problem as outlined above. Typically, this labeling is done by applying channel numbers, alphanumeric codes or symbols to each transmitter and the corresponding receiver or receiver channel. A static assignment, however, has some major disadvantages:                There is no flexibility when using several similar systems simultaneously because a certain transmitter can only be used with its own dedicated receiver or receiver channel. Exchanging transmitters between different systems is not possible.        There is no possibility to replace a defective transmitter with an arbitrary one. The system can only be used again after repairing the faulty device.        The same also applies for the replacement of a receiver.        To get certain flexibility it is necessary to have several systems with identical measurement capabilities to be able to replace a system completely in case of a failure. This, however, increases the overall costs because all systems must have the maximum possible measurement capabilities.        
An automatic channel assignment in a telemetry system is disclosed in EP-A-864293 by the same applicant. A transmitter provides a wireless data transmission with a receiver. For assigning a transmission channel to the transmitter and/or to the receiver, the receiver comprises a receiver contact unit for providing a data communication with a transmitter contact unit of the transmitter. The data communication between the contact units is independent of the wireless data transmission between transmitter and receiver. The channel assignment is executed automatically during a contact phase, wherein the receiver contact unit and the transmitter contact unit are brought into contact.
Although such an automatic channel assignment already represents a major improvement over conventional telemetry systems with manual assignment of transmission channels, a clear assignment and identification between transmitters and receivers is still in the responsibility of the using personnel. In particular in clinical environments, this has been proved to be source of failures, malfunctions, and, worse, misinterpretations of clinical measuring and monitoring results.